Mobile communication method and mobile station

Abstract

A mobile communication method according to the present invention is to communicate between a mobile station (UE) and a radio base station (eNB) by using a certain key generated using a first key. The mobile communication method includes the steps of: updating, at the mobile station (UE), the first key upon receiving a handover command signal from the radio base station (eNB); transmitting, from the mobile station (UE) to the radio base station (eNB), a handover complete signal by using the certain key generated using the updated first key; and performing, at the mobile station (UE), a cell selection processing when failing to transmit the handover complete signal and detecting a radio link failure, and transmitting, from the mobile station to a selected re-establishment target cell, a re-establishment request signal by using the first key before being updated.

1. A mobile communication method for communicating between a mobile station and a radio base station by using a certain key generated using a first key, the mobile communication method comprising the steps of:
 updating, at the mobile station, the first key upon receiving a handover command signal from the radio base station; 
 transmitting, from the mobile station to the radio base station, a handover complete signal by using the certain key generated using the updated first key; and 
 performing, at the mobile station, a cell selection processing when failing to transmit the handover complete signal and detecting a radio link failure, and transmitting, from the mobile station to a selected re-establishment target cell, a re-establishment request signal by using the first key before being updated. 
 
     
     
       2. The mobile communication method according to  claim 1 , wherein
 the handover command signal is an RRC HO Command; 
 the handover complete signal is an RRC HO Complete; and 
 the re-establishment request signal is an RRC Re-establishment Request. 
 
     
     
       3. A mobile station communicating with a radio base station by using a certain key generated using a first key, the mobile station comprising:
 an updating unit configured to update the first key, when receiving a handover command signal from the radio base station; 
 a handover complete signal transmitter unit configured to transmit a handover complete signal to the radio base station using the certain key generated using the updated first key; and 
 a re-establishment request signal transmitter unit configured to perform a cell selection processing when the handover complete signal fails to be transmitted and a radio link failure is detected, and then to transmit a re-establishment request signal to a selected re-establishment target cell by using the first key before being updated. 
 
     
     
       4. The mobile station according to  claim 3 , wherein
 the handover command signal is an RRC HO Command; 
 the handover complete signal is an RRC HO Complete; and 
 the re-establishment request signal is an RRC Re-establishment Request.